1. Field of the Invention
This invention relates to a platinum complex having an antitumor activity and to an antitumor agent comprising the same as an effective component.
2. Description of the Background
Cisplatin, which is a platinum complex reported by Rosenberg et al. as a novel antitumor agent in 1969 [Nature, 222, 385 (1969)] has a wide antitumor spectrum and is used especially as an antitumor agent exhibiting a remarkable effect particularly on genitalia cancer, bladder cancer, head and neck cancer, or the like. There are a number of studies on platinum complexes exhibiting antitumor activities other than cisplatin. Among these platinum complexes those having 1,2-diaminocyclohexane as a ligand are reported in U.S. Pat. No. 4,169,846 (Japanese Patent Laid-open No. 31648/1978) and Japanese Patent Laid-open Nos. 21697/1984, 34982/1985, 97991/1985, 109521/1985, and 59289/1987, and Japanese Patent Publication No. 29957/1983.
Cisplatin is commercially sold as an antitumor agent. However, it has a high toxicity to kidney and other organs, and thus a limitation is imposed to its use. In addition, its water solubility is so small that it can be administered only at an extremely low concentration. This has been a problem for curing diseases using this compound.
(1,2-diaminocyclohexane)malonatoplatinum (II), (1,2-diaminocyclohexane)methylmalonatoplatinum (II), and (1,2-diaminocyclohexane)ethylamalonatoplatinum (II) all disclosed in U.S. Pat. No. 4,169,846 are not necessarily satisfactory in their antitumor activities and water solubility.
Therefore, there has been a strong desire for a platinum complex having a superior antitumor activity and abundant water solubility, and yet possessing a lower degree of toxicity.
In view of this situation, the present inventors have synthesized various platinum complexes having 1,2-diaminocyclohexane as a ligand and studied their pharmaceutical effects, and found that platinum complexes having formula (I) hereinbelow had advantages of superior antitumor activity, abundant water solubility, and lower toxicity. Such findings have led to the completion of this invention.